On 11/07, Paul E. McKenney wrote: > > On Tue, Oct 12, 2010 at 12:08:46AM -0700, Greg Thelen wrote: > > > > ioprio_set() contains a comment warning against of usage of > > rcu_read_lock() to avoid this warning: > > /* > > * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic", > > * so we can't use rcu_read_lock(). See re-copy of ->ioprio > > * in copy_process(). > > */ > > > > So I'm not sure what the best fix is. (please note that "we can't use rcu_read_lock()" actually meant rcu_read_lock() is not _enough_) > I must defer to Oleg, who wrote the comment. But please see below. I added this comment to explain some oddities in copy_process(). Nobody confirmed my understanding was correct ;) In any case, this comment doesn't look right today. This code was changed by fd0928df98b9578be8a786ac0cb78a47a5e17a20 "ioprio: move io priority from task_struct to io_context" after that, tasklist can't help to make sys_ioprio_set(IOPRIO_WHO_PGRP) atomic. I think tasklist_lock can be removed now. And, as Paul pointed out, we need rcu_read_lock() anyway, it was already added by Sergey. Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>